The present invention relates to a method for detecting contamination on a moving object moving in a longitudinal direction past a plurality of detectors. The invention also relates to a measurement apparatus for detecting radioactive contamination of an object, which can move in a longitudinal direction through the measurement apparatus.
It is customary to perform inspections for the transport of radioactive sources at the entrances and exits of nuclear facilities, but also at border crossings, airports, or in general, at entrances and exits of buildings or regions. The inspections performed serve, on the one hand, for protecting people and on the other hand, can also uncover the illegal transport of radioactive material. These two aspects for detecting contamination are combined in the following when speaking of objects to be detected or inspected. Typically the objects to be inspected, which can be people, freight and/or vehicles, are led through a so-called portal monitor, in which detectors for gamma radiation and/or gamma and neutron radiation are provided transverse to the direction of movement.
In the case of a steady flow of objects to be inspected, the portal monitor used can become a chokepoint at which a bottleneck forms. In the case of inspecting people at entrances and exits, wait times arise. Also with container inspections, for example, at ports, the wait time can result in a slow-down in the processing of containers. The required measurement time for an object in a portal monitor depends directly on the required detection limit of the monitor. In the case of a low detection limit, a sensitive monitor can handle a higher flow-through of objects per unit of time, wherein the use of sensitive monitors is naturally associated with higher costs.